Tuesday, October 1, 2013

The Science in the 2013 IPCC Report: Unequivocal Evidence of Anthropogenic Climate Change

The huge new climate report from the U.N. Intergovernmental Panel on Climate Change (IPCC) states with more clarity than ever before that humans are to blame for climate change.

"Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia."

With 95 percent certainty (up from 90 percent in 2007, 66 percent in 2001 and 50 percent in 1995) scientists attribute climate change to human activities, especially burning fossil fuels.  The IPCC further states that humans have most likely caused all of the global warming over the past 60 years.

As it enters its third decade of existence, the IPCC is the undisputed global authority on climate change. With more than 50,000 comments the AR5 WGl report is amongst the most intensively reviewed scientific documents ever to be published.

“I know of no other document that has undergone this scrutiny,” Thomas Stocker, co-chair of the working group said. “It stands out as a reliable and indispensable source of knowledge about climate change.” The 2013 IPCC report says essentially the same thing as the 2007 IPCC report, only it does so with an even greater degree of confidence. It offers the strongest evidence ever that burning fossil fuels is the cause of most of the temperature increases of recent decades.

We already observe higher concentrations of greenhouse gases in the atmosphere, warmer land and ocean temperatures, as well as melting polar ice and glaciers. The impacts from these temperature increases will include a sea level rise of almost three feet by the end of the century if we continue with business as usual. In practical terms this means cities like New York, Miami and Shanghai will be flooded while droughts will cause widespread famine in Africa, and millions of refugees fleeing climate-related catastrophes.

Other salient findings in the report include the observation that each of the last three decades has been warmer at the Earth’s surface than any previous decade since 1850. In the Northern Hemisphere, 1983–2012 was “likely” the warmest 30-year period of the last 1400 years.

Governments have internationally agreed that global temperature rise must not surpass two degrees Celsius above pre-industrial levels. However we are on track to eclipse that number if we continue with business as usual. Research from Carbon Tracker and the World Bank warn that the current level of government action means the world is on track to warm by around three degrees Celsius this century; the IPCC concur. The average global warming of 0.8 degrees Celsius from pre-industrial levels is already affecting the lives of billions of people.

Extreme weather events like torrential rains, droughts and floods, are already having massive social impacts and costing as much as $1.2 trillion every year. The economic costs and the cost in human lives will continue to increase as the planet continues to warm.

As explained by Thomas Stocker, co-chair of the IPCC working group, limiting climate change will require “substantial and sustained” GHG reductions. As the head of the IPCC, Rajendra Pachauri, recently said, governments must act now to cut carbon pollution: "We have five minutes before midnight."

© 2013, Richard Matthews. All rights reserved.

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